1. Field of the Invention
The present invention relates to a push button switch and, more particularly, to a push button switch suitable for use in a terminal machine of a computer or in an electric typewriter.
2. Description of the Prior Art
Generally speaking the push button switch of the kind mentioned above has, as disclosed in the specification of U.S. Pat. No. 3,969,600, an inversion leaf spring member made of a thin plate of beryllium copper or the like material is disposed on the bottom plane so as to extend in a horizontal plane. In operation, the inversion leaf spring member is inversed as it is depressed vertically by a depression of key top, so as to bring the movable contact into contact with a fixed contact, thereby to close the switch.
This switch however has disadvantages such as a limited stroke of the keytop. In addition, the contact mechanism is so weak that it may be broken by a large depressing force exerted on the key top.
In order to avoid the breakage of the contact mechanism, U.S. Pat. No. 3,773,998 proposes a push button switch incorporating a coiled spring. This switch, however, cannot provide a distinctive feel to the user of the switch.